1. Field of the Invention
This invention relates to catheter-based implantable medical devices for occluding the flow of blood at a preselected position within a blood vessel, and more particularly to an aneurysm embolic device which serves to fill an aneurysm with an occlusive member thereby preventing the flow of blood into the aneurysm.
2. Description of the Prior Art
Aneurysms typically take the form of a balloon-like swelling in the wall of a vessel which generally results from a weakness in the vessel wall. If untreated, aneurysms may continue expanding until they burst thereby causing hemorrhaging to occur. If, for example, an aneurysm is present within an artery of the brain, and the aneurysm should burst with resulting cranial hemorrhaging, death could occur.
Aneurysms result from many different causes; however, most aneurysms are caused as a result of a degenerative disease which damages the muscular coating of a vessel with resulting congenital deficiency in the muscular wall of the vessel.
Various attempts have been made to treat aneurysms without resorting to surgery, such as the placement of sleeves or stents into the vessel and across the region where the aneurysm occurs. Such devices maintain blood flow through the vessel while reducing blood pressure applied to the interior of the aneurysm. Certain types of stents are expanded to the proper size by inflating a balloon catheter, referred to as balloon expandable stents, while other stents are designed to elastically expand in a self-expanding manner. Balloon expandable stents and self-expanding stents are generally delivered to a preselected position through a delivery catheter. They are moved out of the distal end of the delivery catheter, are expanded and then are released to remain within the vessel. One example of a delivery catheter system which may be used to place a stent within a vessel is disclosed in U.S. Pat. No. 6,254,612 entitled, “Hydraulic Stent Deployment System” and assigned to the same assignee as the present patent application. The stent deployment system disclosed in this patent, which is incorporated herein by reference, includes a deployment catheter having a distal tip for retaining a stent in order to transport the stent to a preselected position within the vessel. Once the stent has been properly positioned, a hydraulic control mechanism is used to release the stent from the distal end of the catheter and deposit the stent at the preselected location within the vessel.
Another method for treating aneurysms, particularly where the aneurysm occurs in a very small vessel of the brain, is that of using a microcatheter for placing multiple very small embolic coils within the aneurysm with the expectation that fibrous material will become entrapped in the embolic coils to thereby stabilize the coils within the aneurysm. With this technique, it is possible to fill the aneurysm with embolic coils thereby sealing off the walls of the aneurysm from the pressure of blood which exist in the adjacent vessel.
Examples of a catheter deployment system for depositing embolic coils into an aneurysm are disclosed in U.S. Pat. No. 6,063,100, entitled, “Embolic Coil Deployment System With Improved Embolic Coil”; U.S. Pat. No. 6,183,491 entitled, “Embolic Coil Deployment System With Improved Embolic Coil”; and U.S. Pat. No. 6,113,622 entitled, “Embolic Coil Hydraulic Deployment System,” all of which are assigned to the assignee of the present patent application. These patents, and the disclosure thereof, are incorporated herein by reference and made a part of the present patent application.
One modification to the technique of placing embolic coils within an aneurysm is that of using a stent or scaffold like structure which is placed across the aneurysm by having passageways within the structures so that embolic coils may be passed through the structure and into the aneurysm. The stent, or scaffold like structure, serves to hold the embolic coils within the stent until such time as these coils become stabilized by fibrous material growing into the coils. One example of such a structure, or stent, for use in this form of treatment of an aneurysm is disclosed in U.S. Pat. No. 6,063,111 entitled, “Stent Aneurysm Treatment System And Method.”
Still another method of treating an aneurysm, and in particular an aneurysm within the brain, is that of placing a mesh covered support structure within the aneurysm itself and subsequently expanding the mesh covered structure in order to fill the entire aneurysm. Such a structure serves to fill the aneurysm and thereby prevent blood flowing in an adjacent vessel from entering the aneurysm. These devices, referred to as occlusion devices, serve to prevent the pressure of blood flowing through a vessel from being applied to the walls of the aneurysm thereby preventing, or reducing, the further expansion of the aneurysm.
One such aneurysm occlusion or embolization device is disclosed in U.S. patent application Ser. No. 09/505,231 entitled, “Aneurysm Embolization Device,” and assigned to the same assignee as the present patent application.
Even with the existing treatment techniques for aneurysms, and in particular for aneurysm which exists within the brain, there is a need for other forms of aneurysm treatment that may be easily delivered to a vascular site through a very small catheter, and in particular for a device which serves to seal off the flow of blood between an adjacent vessel and an aneurysm.